I'm using Shell Rotella T 15W40 CI-4Plus in most of my Fleet Rentals. Why? Because it cheaper than most CI-4 oils and readily available coast to coast. These units are powered with DTs466E and 570s, C-9s through C-15s in my class 8 rigs. My MBE 9000 in medium duty diggers and buckets get Rotella T for the same reason. Now, around the farm I using Rotella T in three of my Kubota D782-Es and Delo 400 CI-4 plus in one D902E and my new toy V3800-DI-T-ES. I also use Delo 400 in my personal 5.9 ISB Cummins, why, because I refuse to purchase the preminum Super Blue formulated by Cummins Engineers because of the cost involved to refine it in Ashland, KY. (Valvoline/Marathon). Years ago I would purchase the 55 gallons drums of Super Blue for all my Cummins and did notice a difference in valve train wear as a result of it's use. Soot is your number one enemy in a diesel engine on all valve train components. Without a doubt, Rotella Ts additives suspends soot with good intension to remove it from your engine during an oil change. I'm out to school on oil samples on either oils thus mentioned. Both hold up well under the extreme pressures experencied during high torque demand on dynometers. Personally, without the aid or testing using samples on a spectrograph, I feel the Delo 400 compared to Shells Rotella T, is a better refined product containing less ash. It seems to stay cleaner than Shell's product between oil changes. Just my opinion from an old wrench.